Water Supply Systems

Marine sprinkler systems are initially charged with a primary supply of fresh water from a cylindrical pressure tank. The average pressure tank has a capacity of 2979 litres. The normal fill is about 1500 litres.

Tank pressure is obtained by pumping air into the tank. The air supply delivery pipe incorporates a check valve and stop valve. Tank pressure is maintained at approx 8.3 bar. The pressure tank delivery connection to the trunk main is fitted with two stop valves, a non-return valve and a drain valve. The stop valves should normally be strapped open. The non-return valve prevents the admission of salt water into the pressure tank.

A level gauge is fitted to the tank to ensure the required level of water is maintained. The fresh water supply is usually taken from the vessel's portable water system through a 40mm feed pipe, fitted with a stop valve and check valve.

Where fresh water and/or compressed air are not available on board the ship, a dedicated “sea water” pump and compressor can be supplied. The pump has an average flow capacity of about 1530 l/min. On large passenger ships, marine regulations may require both a primary fresh water supply and an additional “sea water” supply.